This application claims the priority of German Patent Application Serial No. 100 20 066.4, filed Apr. 22, 2000, the subject matter of which is incorporated herein by reference.
The present invention relates to a connector for coaxial cables with thin-walled outer cable conductor.
Coaxial cables with thin-walled outer cable conductor are oftentimes called sheet-type cables, whereby the outer cable conductor may be made, for example, of overlapping wound copper foil or of a very thin, longitudinally welded copper tube. As so-called radiating cable, the thin and thus mechanically sensitive outer cable conductor is formed in addition with holes or openings at uniform distances. Used for these types of coaxial cables are typically connectors with a connector head that forms the outer connector conductor and embraces a support insulator for centered disposition of an inner connector conductor, as well as a contact sleeve for establishing a contact between the outer cable conductor and the connector head. The contact sleeve has a thin, cable-proximal threaded portion for rotation into the cable either between the outer cable conductor and the cable dielectric or between the cable sheath and the outer cable conductor. On the outside or inside, the contact sleeve may have a small barb.
Installation of conventional connectors of this type on respective coaxial cables is tedious as outer cable conductors typically have significant tolerances as far as diameters are concerned and oftentimes are not exactly round. As a consequence, the thin-walled outer cable conductor is pushed back or can rupture during insertion or rotation of the contact sleeve into the cable, and thus is more or less destroyed in the assembly area. A faulty contact is hereby only difficult to ascertain from outside as the cable sheath encloses the outer cable conductor.
It would therefore be desirable and advantageous to provide an improved connector which obviates prior art shortcomings and which is easy to attach to coaxial cables, also to coaxial cables with mechanically sensitive outer cable conductor that can easily be damaged, without risk of destruction of the outer cable conductor.
According to one aspect of the present invention, a connector for a coaxial cable with thin-walled outer cable conductor; includes a connector head forming an outer connector conductor for electric connection to an outer cable conductor of a coaxial cable, an inner connector conductor, a support insulator received interiorly of the connector head for holding the inner connector conductor centrally in and spaced from the connector head, a contact sleeve surrounded by the connector head for establishing a contact between the outer cable conductor and the connector head, wherein the contact sleeve has a thin-walled cable-proximal portion formed with a thread and intended for rotation into the coaxial cable for establishing the contact between the outer cable conductor and the connector head, and wherein the contact sleeve has a cable-proximal end edge formed with at least one protrusion projecting in an axial direction in the direction of the cable to establish an expanding mandrel.
During assembly, a rotation of the connector head, when the contact sleeve is in fixed rotative engagement within the connector head, or a rotation of the contact sleeve only, generates a ring-shaped gap which, depending on the diameter of the contact sleeve, may be formed either between the cable dielectric and the outer cable conductor or between the outer cable conductor and the cable sheath. The threaded portion of the contact sleeve can then be rotated completely into this forming gap, without risk of damage to the outer cable conductor. The connector includes thus an integrated expanding mandrel.
Penetration of the protruding sleeve portion, i.e. expanding mandrel, can be further facilitated when configuring the expanding mandrel with a chamfered leading edge, whereby the leading edge should, however, remain rounded and thus should not have any sharp areas.
According to another feature of the present invention, the outer thread of the thin-walled portion of the contact sleeve may be configured to commence at the cable-proximal end edge in circumferential direction approximately in vicinity of the trailing edge of the protruding sleeve portion. As a consequence, a guidance of the contact sleeve is ensured when the contact sleeve begins to penetrate the ring-shaped gap or space as created by the expanding mandrel.
According to another feature of the present invention, the cable-proximal end edge of the contact sleeve may be configured to follow a first thread turn up to the root of the leading edge. Thus, the cable-proximal end edge of the contact sleeve is not positioned in a radial plane but extends in accordance with the pitch of the thread. Also, in this way, a xe2x80x9cbluntxe2x80x9d penetration of the contact sleeve into the gap created by the expanding mandrel is prevented.
According to another feature of the present invention, the contact sleeve may be formed with an annular shoulder for abutment of a cable sheath of the coaxial cable. In this way, the contact sleeve and thus the entire connector have a defined position with respect to the end face of the cable after assembly. Suitably, the contact sleeve may also have an internal annular shoulder for abutment of a confronting end face of a cable dielectric.
For coaxial cables with tubular inner cable conductor, a connector according to the invention may be so configured that the inner connector conductor is extended beyond the cable-proximal end edge of the contact sleeve to provide a leading centering piece for insertion of the contact sleeve. To compensate a possible slight eccentricity of the outer cable conductor with respect to the hollow inner cable conductor, when starting to mount the connector to the cable as a result of a tilting of the outer cable conductor by hand, and thus to ensure that the expanding mandrel penetrates the cable at the intended area, the inner connector conductor may have a portion of reduced diameter disposed inwardly of the centering piece. This centering function is thus assumed by the inner connector conductor during assembly, and can be further enhanced by providing the inner connector conductor with a radially resilient contact member disposed inwardly of the centering piece.
A stable contact over an extended period even when the transition between cable and connector is exposed to mechanical stress, and a reliable protection from ingress of moisture can be realized when disposing in the recess of the connector head an elastic sealing ring and a thrust ring positioned next to the sealing ring and braced with the connector head by a clamping member so that the sealing ring is axially compressed after assembly of the connector to thereby force the cable sheath radially against the contact sleeve. The contact sleeve acts as abutment for the cable sheath which thereby, optionally together with the outer cable conductor, is clamped between the sealing ring and the wall of the contact sleeve. This construction ensures that in particular tension forces are transmitted from the cable primarily via the cable sheath to the connector and not, as is typically the case in conventional connectors, via the outer cable conductor which is extremely sensitive and thus incapable to absorb tension forces, when configured for sheet-type cables.
According to another feature of the present invention, the clamping member may be a clamping bush having at least one recess for allowing visual inspection of the expanding mandrel of the contact sleeve, when the clamping bush occupies a predetermined rotation position with respect to the connector head.